The present invention relates to an ultrasound therapy system which obtains a tomogram of biological tissue and effects the treatment of an affected part.
Recently, various therapy systems using ultrasound, have been developed. On example is hyperthermia treatment, which is one method of treating malignant neoplasm, generally called cancer. Tumors are more sensitive to temperature than healthy tissue. Tumorous tissue dies or does not propagate if it is subjected to a temperature of 42.5.degree. C. or more. The treatment based on this phenomenon is called the hyperthermia treatment. Many clinical examples have shown that hyperthermia treatment effectively restricts the growth of various types of tumorous tissue and even reduces tumorous tissue.
Many types of hyperthermia treatment are known. Of these methods, local hyperthermia treatment is particularly effective.
Local hyperthermia treatment using electromagnetic waves such as microwaves has been proposed and put into practice. This method, however, has one major disadvantage. That is, it is very difficult to accurately heat deep tumors. This is due to the attenuating characteristic of electromagnetic waves having wave lengths suitable for the hyperthermia treatment. (This characteristic depends on the electromagnetic wave length.) In this treatment, examples of effective hyperthermia treatment are limited to surfacial tumors located within about 5 centimeters of the epidermis.
To solve this problem, another method of hyperthermia treatment has been studied and proposed. This method features ultrasonic waves instead of electromagnetic waves. This is because ultrasonic waves can cause vibration.
Ultrasonic waves are also used to treat calculi such as renal calculi or urinary calculi. In this treatment, high ultrasound beams can be focused on a calculus and effect spallation.
Such ultrasonic treatment requires one of two types of ultrasound transducers. One type of transducer includes a plurality of ultrasound transducer elements 1 each having a concave spherical ultrasound radiation surface, which are arrayed on a concave spherical surface, as shown in FIGS. 1A and 1B. The second type of transducer is annularly arrayed such that a plurality of ring shaped transducer elements 2 are concentrically arrayed as shown in FIGS. 2A and 2B. Both types of transducers focus ultrasound waves on a deep target portion P to effect treatment.
The second type of transducer, i.e. an annular array ultrasound transducer, has especially attractive advantages. With this type of transducer, ultrasound beams can be accurately focused on a deep target, and the distance from the transducer to the point of focus can be electrically varied.
In a conventional system of this type, recognition of the position and configuration of the target to be treated is executed by a diagnostic apparatus for checking and diagnosing a state and location of specific tissue in a patient. To treat a tumor, however, another apparatus is required. As a result of using different apparatuses, healthy tissue is frequently treated. Naturally, this is undesirable. In this respect, this method does not permit utilization of the high capacity to focus ultrasound beams, which prevents maximum treatment of diseased tissue. The need for two types of apparatuses also makes treatment complicated and cumbersome. One example is positioning the ultrasonic transducer.